Ooh!! I know this one!! I'm studying it right now in history, lmao, they ate alot of bread. They ate this because they grew alot of wheat in the middle colony's due to kinda fertile soil and short growing seasons, so it was easy to grow wheat and produce grain. :D they're also nicknamed the Bread Basket colonies
They ate bread (A baked form of wheat), corn, what they could get from the cattle (Cheese , and butter and goat preferably dairy (Milk) due to the fact that fresh cow milk made the colonists sick. And because the milk of a cow was thick and full of fat, thus it was hard to refine enough to where it wasn't all fat).